Divide everything by 4 getting:
7y=3x+21
then get all of the variables on one side by subtracting 3x:
7y-3x=21
The answer is 10 because 9x5=45 then you do 45-15=30 then you divide by 3 which is 10.
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Answer:

Step-by-step explanation:
Area of triangle = 0.5 × Base × Height
→ Substitute in the values
200 = 0.5 × 5x × 5x
→ Simplify
200 = 12.5x²
→ Divide both sides by 12.5
16 = x²
→ Square root both sides
4 = x ∴ x = 4
30% of 10,000 is 3,000, so the salesperson would have sold the boat for $13,000. The difference between the auction price and dealership price is 3,000. The commission is 25% of 3,000, which is $750.
Answer:

Step-by-step explanation:
n is doubled: 2n
y added: 2n + y
divided by 2: n + 
n subtracted -> final resutl: 